1. Field of the Invention
The present invention relates to an apparatus and method for controlling the tilt of an imager to allow alignment to a specimen, while permitting a hard-dock to a tester connected to the specimen.
2. Description of the Related Art
Many optical systems for inspection of specimen, such as substrates, exist in the prior art. One such system is described in U.S. Pat. No. 6,621,275, which is assigned to the current assignee and which is incorporated herein by reference in its entirety. Such systems can be used for inspection or testing and debug of semiconductor substrates or integrated circuits. Examples of systems for imaging flip-chip type integrated circuits through the silicon substrate are described in U.S. Pat. Nos. 5,208,648, 5,220,403 and 5,940,545, which are incorporated herein by reference in their entirety.
FIGS. 1A and 1B are general schematics depicting major components of an arrangement of an Automated Testing System (ATE) connected to an emission testing and debug system (Such as the Sapphire™ and the EmiScope™, respectively, available from Credence Systems, Inc. of Milpitas, Calif.) that is helpful for the understanding of the present invention. A system that is similar to the EmiScope is described in co-assigned U.S. patent application Ser. No. 10/912,896 which is incorporated herein by reference in its entirety. As will become apparent from the description, this arrangement is used to illustrate the features of the invention; however, the invention is not limited in its applicability to such an arrangement and is rather useful in various other systems and arrangements.
In FIGS. 1A and 1B, the ATE 100 is shown with its tester head 110 extended over the emission tester 150, so as to connect to a device under test (DUT) 130 via flexible connector 115. The tester head 110 is movable for docking using manipulation arm 105. The ATE 100 generally comprises a controller, such as a pre-programmed computer 105, that generates and delivers test signals to the DUT 130 in a manner well known in the art. Specifically, the ATE 100 is used to generate signals that stimulate the DUT 130 to perform various tasks, as designed by the chip designer to check and/or debug the DUT 130. The various signals generated by the controller 105 are delivered to the DUT 130 via the connector 115. As is well known in the art, as the DUT 130 reacts to the various test signals received from the ATE, the DUT's various active elements emit light. The light is then detected by the emission tester 150 and is used by the emission tester 150 to decipher the operation of the DUT 130.
On the emission tester side, the DUT 130 is held on an adapter plate 155, which is connected to a self-leveling, vibration-isolation bench 160 via tilting mechanism 165. The tilting mechanism 165 can be implemented using servomotors, or in other manners as described more fully in the above-cited co-assigned patent application. While only one tilting mechanism is shown, it should be appreciated that several can be used so as to obtain the appropriate degrees of freedom for the required tilting. The bench 160 can be any commercially available self-leveling vibration-isolation bench (e.g., the Precision-Aire™available from Fabreeka™ of Boston, Mass. or an Optical Table 5000 series, available from Kinetic Systems, Inc. of Boston Mass.). Such a bench generally includes a tabletop 175 riding on plungers 170. Each plunger 170 is operable, pneumatically, for example, to rise or drop so as to level to tabletop 175. A level control valve 180 is used to control the plunger so as to provide automatic leveling of the tabletop 175. An x-y-z stage 185 is connected to the underside of the tabletop 175. The stage 185 is used to support and navigate the collection optics 190 so as to collect light from the DUT 130. The collection optics may include an objective lens and a solid immersion lens (SIL), in a manner known in the art. The various elements of the emission tester are controlled by a controller 195 via connector 120, which may be a general purpose computer pre-programmed to perform specific tasks.
As can be understood, for maximum light collection efficiency, the inspected surface of the DUT 130 needs to be orthogonal to the optical axis of the collection optics 190. To achieve that, the tilt mechanism 165 is operated so as to tilt the adapter plate 155 as shown by the double-headed arrow, so as to achieve the required alignment. In FIG. 1A the adapter plate 155 is shown leveled with the tabletop 175, while in FIG. 1B the adapter plate 155 is shown tilted with respect to the tabletop 175. However, while the tilt mechanism 165 is operable to tilt the adapter plate 155, as shown in FIG. 1B the tester head 110 is stationary and does not move with the adapter plate 155. Therefore, in the prior art, a flexible connector 115 is used to maintain the connections between the tester head 110 and the DUT 130. However, the use of such a flexible adapter introduces several drawbacks to such an arrangement. Such flexible adapters are complex and expensive. Additionally, in order to obtain accurate testing, each such flexible adapter needs to be accurately characterized, which adds to the cost of the arrangement. Regardless of characterization, the flexible adapter may introduce inaccuracies into the testing. Moreover, the adapter may be exposed to repeated stresses due to repeated tilting and may fail prematurely.
Accordingly, there is a need in the art for a system that will allow docking of the tester head to the DUT without a flexible adapter, i.e., hard docking, while still maintain the ability to align the DUT to the optical axis of the collection optics.